Predicting the Impact of Red Winemaking Practices Using a Reactor Engineering Model

Red wine fermentations have long eluded accurate simulation because of their inhomogeneous nature. In this work, a three-dimensional, time-dependent, reactor engineering model for jacketed red wine fermentations was utilized to explore the effect of fermentor volume (500; 50,000; and 500,000 L), aspect ratio (height: diameter of 1: 1 and 3: 1), temperature set point (15, 25, and 35 degrees C), and initial yeast assimilable nitrogen (YAN) concentration (100, 225, and 350 mg/L) on fermentation dynamics. The model simulated N-limited, ethanol-inhibited, and temperature-dependent Monod fermentation kinetics; mass transfer of sugar, yeast, N, and ethanol; evaporative, convective, and conductive heat transfer; and the motion of the bulk fluid beneath the cap. Fermentor surface area-to-volume ratio, temperature set point, and initial YAN were all found to significantly affect fermentation performance in simulated fermentations. Heat transfer by conduction into the cap was nondimensionalized and analyzed as well. Finally, the formation of temperature gradients in the cap between cap-management cycles was visualized from simulations using the model.